Best known today as the centerpiece of interactive costume parties, this amalgam of science fiction, classic horror and glam rock follows a clean-cut couple (Barry Bostwick and Susan Sarandon) who wander into the castle of the vamping, sexually ambiguous, bustier-favoring alien Dr. Frank-N-Furter (Tim Curry). Partly a sendup of conservative tradition, partly a gay pride parade that’s taken a few detours, the movie nevertheless feels about as outre as a teen boy who dabbles in mascara. It isn’t out to shock as much as have its own brand of fun, making it clear all along that anyone is welcome to join in.